This is a note to let you know that I've just added the patch titled
bcache: Fix a dumb race
to the 3.10-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bcache-fix-a-dumb-race.patch
and it can be found in the queue-3.10 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 6aa8f1a6ca41c49721d2de4e048d3da8d06411f9 Mon Sep 17 00:00:00 2001
From: Kent Overstreet <kmo@xxxxxxxxxxxxx>
Date: Wed, 10 Jul 2013 18:04:21 -0700
Subject: bcache: Fix a dumb race
From: Kent Overstreet <kmo@xxxxxxxxxxxxx>
commit 6aa8f1a6ca41c49721d2de4e048d3da8d06411f9 upstream.
In the far-too-complicated closure code - closures can have destructors,
for probably dubious reasons; they get run after the closure is no
longer waiting on anything but before dropping the parent ref, intended
just for freeing whatever memory the closure is embedded in.
Trouble is, when remaining goes to 0 and we've got nothing more to run -
we also have to unlock the closure, setting remaining to -1. If there's
a destructor, that unlock isn't doing anything - nobody could be trying
to lock it if we're about to free it - but if the unlock _is needed...
that check for a destructor was racy. Argh.
Signed-off-by: Kent Overstreet <kmo@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/md/bcache/closure.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
--- a/drivers/md/bcache/closure.c
+++ b/drivers/md/bcache/closure.c
@@ -66,16 +66,18 @@ static inline void closure_put_after_sub
} else {
struct closure *parent = cl->parent;
struct closure_waitlist *wait = closure_waitlist(cl);
+ closure_fn *destructor = cl->fn;
closure_debug_destroy(cl);
+ smp_mb();
atomic_set(&cl->remaining, -1);
if (wait)
closure_wake_up(wait);
- if (cl->fn)
- cl->fn(cl);
+ if (destructor)
+ destructor(cl);
if (parent)
closure_put(parent);
Patches currently in stable-queue which might be from kmo@xxxxxxxxxxxxx are
queue-3.10/bcache-fix-a-dumb-race.patch
queue-3.10/bcache-advertise-that-flushes-are-supported.patch
queue-3.10/bcache-fix-gc_sectors_used-calculation.patch
queue-3.10/bcache-shutdown-fix.patch
queue-3.10/bcache-journal-replay-fix.patch
queue-3.10/bcache-fix-a-sysfs-splat-on-shutdown.patch
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